The need frequently arises for valving apparatus to alternately pressurize and relieve a fluid chamber. For example, the need arises for such valving apparatus in dispensing guns, as for paste, mastic and other flowable substances. Connected to a source of air under pressure, such a three-way valve has three states. In the quiescent state, the gun is relieved and the pressure source is isolated. In an intermediate state, a relief passage is closed while the pressure source is still isolated. In the third state, the relief passage is closed and a pressure passage is open for pressurizing the dispensing gun. Usually after an interval of operation, the sequence is reversed returning the valve to the quiescent state in which the pressurizing passage is closed and the relief passage is open. Again to avoid blow off, the pressure passage is closed before the relief passage is opened.
A variety of three-way valve arrangements for operation as described above have been previously proposed. Some such prior structures incorporated a conventional pneumatic tire valve core. Specifically for example, such valves are disclosed in U.S. Pat. Nos. 2,838,210 and 3,237,814. However, in spite of the development of such prior devices, a need continues to exist for an economical, durable and effective three-way valve for use in pressuring-relieving applications.
In general, the present invention incorporates a conventional pneumatic tire valve mounted for cooperative movement and operation with a resiliently deformable member affording a second valve closure to accomplish three-way operation. A simple support structure defines valve ports, serves as a seat for the resiliently deformable member and mounts a set screw to actuate the pneumatic tire valve core.